Mixer and exhaust system

Abstract

A static mixer for the through-mixing of a flow in a line conducting the flow, more preferably of an exhaust system of a combustion engine with several guide vanes. To create adequate through-mixing at low flow velocity and a through-flow resistance that is not too high at high flow velocity, the guide vanes are produced of a shape memory alloy wherein below a predetermined limit temperature the guide vanes have at least one low-temperature shape and above the limit temperature the guide vanes have at least one high-temperature shape, which differs from the low-temperature shape through a reduced through-flow resistance of the mixer.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application claims the benefit of priority under 35 U.S.C. §119 of German Patent Application 10 2010 021 040.4 filed May 19, 2010, the entire contents of which are incorporated herein by reference.FIELD OF THE INVENTION[0002]The present invention relates to a static mixer for the through-mixing of a flow in a line conducting the flow, particularly of an exhaust system of a combustion engine, the static mixer including several guide vanes. The invention additionally relates to an exhaust system for a combustion engine equipped with such a mixer, more preferably of a motor vehicle.BACKGROUND OF THE INVENTION[0003]In many technical fields it is required to homogenize a multi-phase flow. To this end, a mixer can be arranged in a stationary manner in a line conducting the flow, through which mixer the flow flows and in the process mixes the individual phases of the flow, which leads to the desired homogenization. Such a mixer arranged in ...

AI Technical Summary

Benefits of technology

[0008]The present invention deals with the problem of providing an improved embodiment for a static mixer or for an exhaust system equipped with such, which is more preferably characterized in that the mixer on the one hand has an adequate mixing effect even at lower flow velocities while on the other hand it has a reduced through-flow resistance, particularly at higher flow velocities.

[0009]The invention is based on the general idea of producing the guide vanes of the mixer from a shape memory alloy namely in such a manner that they at least comprise one low-temperature shape and at least one high-temperature shape, which for the mixer create different through-flow resistances. Below a predetermined limit temperature the guide vanes have a low-temperature shape that has a comparatively high through-flow resistance. Above the predetermined limit temperature the guide vanes have a high-temperature shape which has a comparatively low through-flow resistance. The high through-flow resistance, with corresponding configuration of the guide vanes, is accompanied by a higher mixing effectiveness. In this manner it is ensured that below the limit temperature an effective mixing of the flow takes place. The effectiveness of the mixing with low flow-through resistance is correspondingly reduced. The present invention is based on the realization that the exhaust gas temperature on the one hand correlates with the load of the combustion engine and on the other hand also with the rotational speed of the combustion engine. This means that at high flow velocities high exhaust gas temperatures also occur as a rule, while comparatively cold exhaust gases regularly occur only at low flow velocities. At high flow velocities a mixer with reduced mixing effect can also achieve an adequate mixing of the flow. At the same time, the high exhaust gas temperatures improve the droplet evaporation and consequently reduce the danger of a droplet strike-through.

Problems solved by technology

The use of such mixers in the exhaust system however is problematic.

At higher flow velocities, this leads to a considerable drop in power of the combustion engine.

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